The alleged shooter in the attack on the Capital Gazette newspaper has been tentatively identified as Jarrod Warren Ramos of Laurel, Maryland, according to multiple law enforcement sources.

Ramos is charged with five counts of first-degree murder. At his bail hearing on Friday morning, he was denied bond.

Tom Marquardt, retired publisher and top editor at the paper, told the Capital Gazette that he'd called Anne Arundel County Police years ago over worries about Ramos' attacks on the paper and its journalists on social media.

"I was seriously concerned he would threaten us with physical violence," Marquardt said. "I even told my wife, 'We have to be concerned. This guy could really hurt us.'"

Here is what we know so far about Ramos:

THE CAPITAL GAZETTE WROTE ABOUT RAMOS

In 2011, the paper published a story about allegations Ramos stalked an ex-girlfriend, Marquardt said. The article was published five days after Ramos pleaded guilty to criminal harassment, according to the Associated Press.

In the article, the woman said that Ramos had reached out to her on Facebook to say that she had been the only person who had been kind to him in school. Feeling that he might be experiencing some problems, the woman had encouraged him to seek counseling. That set off months of emails in which he alternatively asked for help and was nasty to her, she said. He called her vulgar names and even told her to kill herself, the woman told the paper.

RAMOS THREATENED THE PAPER ON SOCIAL MEDIA

After the article was published, Ramos sued the paper, beginning a long legal fight that Marquardt said was tame compared to his taunts and threats on social media.

Ramos directed scores of profanity-laced tweets at the paper's journalists, AP reports. At least one tweet was directed at columnist and editor Rob Hiaasen, one of the victims killed on Thursday.

In a different tweet, Ramos said he'd enjoy seeing the paper stop publishing, but "it would be nicer" to see two journalists "cease breathing."

When Marquardt called the police in 2013, they investigated and even visited Ramos at his home but did not have enough to charge him.

RAMOS HAD A HISTORY WITH THE COURTS

2011: Ramos pleaded guilty in the criminal harassment case the Capital Gazette would then write about. Also in 2011, a peace order -- an order issued by a judge to stay away from someone and to avoid contacting them -- was filed against Ramos.

2012: Ramos filed a lawsuit against the paper, alleging it contained false and defamatory statements that injured his reputation. During the court case, the judge asked him to point out one statement in the article that was false and defamatory, but he couldn't name one. The case was dismissed, and an appeals court upheld the dismissal.

Also in 2012, another peace order was issued against Ramos.

2013: Ramos filed a lawsuit against Anne Arundel County District Judge John McKenna. Online court records did not indicate the nature or result of that suit.

Also in 2013, yet another peace order was issued against Ramos.

2014: Ramos sued three people. That case was dismissed when Ramos failed to show up for court two years later.

Ramos appealed at least two of the three peace orders filed against him. It wasn't clear whom the cases involved or what the ultimate outcomes were.

WHAT HAPPENED THURSDAY

Investigators said the suspect, armed with a shotgun, entered the Capital Gazette office and deployed smoke grenades. The suspect then opened fire, killing five people and gravely wounding several others in what authorities called a "targeted attack."

Acting Police Chief William Krampf of Anne Arundel County says it was a targeted attack in which the gunman "looked for his victims."

Phil Davis, a reporter who covers courts and crime for the Capital Gazette, tweeted that the gunman shot out the glass door to the office and fired into the newsroom, sending people scrambling for cover under desks.

Gunman shot through the glass door to the office and opened fire on multiple employees. Can't say much more and don't want to declare anyone dead, but it's bad.

Authorities responded within minutes, and the suspect was taken into custody without an exchange of gunfire.

Anne Arundel County Executive Steve Schuh told ABC News the suspected gunman was found by police hiding under a desk in the newsroom and was apprehended there.

POLICE HAD TROUBLE IDENTIFYING RAMOS

Authorities said he was not carrying identification at the time of his arrest and was not cooperating.

Though early reports indicated that Ramos had mutilated his fingers to thwart attempts to identify him, a local law enforcement official later told ABC News that an issue with the fingerprint machine ultimately made it difficult to identify the suspect, and there was no mutilation.

A source said officials used facial recognition technology to confirm his identity.

The suspect had previously only been publicly described as a white male in his late 30s who is a Maryland resident.

Court documents filed on Friday show Jarrod W. Ramos was charged in the shooting.

WHAT ELSE WE KNOW ABOUT RAMOS

In the 2011 article, Ramos was described as a tall, thin man with long hair worn in a ponytail. His lawyer told the newspaper that Ramos has a degree in computer engineering and had worked for the U.S. Bureau of Labor Statistics for six years. His lawyer also said Ramos had no previous criminal record.